Bias constructed truck tire



Aug. 20, 1968 L. R. SPERBERG BIAS CONSTRUCTED TRUCK TIRE Filed Oct. 24,1965 IN VEN TOR. LAWRENCE R. SPERBERG BY' MARCUS L. BATES United StatesPatent O 3,397,729 BIAS CONSTRUCTED TRUCK TIRE Lawrence R. Sperberg, Box12308, El Paso, Tex. 79912 Filed Oct. 24, 1965, Ser. No. 504,768 8Claims. (Cl. 152-354) ABSTRACT OF THE DISCLOSURE Nylon, as used herein,relates to a synthetic textile comprised of a polyamide resin. Rayonrelates to a synthetic textile comprised of a modified cellulosefilament, including the (extra high modulus) material as well as Tyrex.

Nylon has gradually replaced rayon as the principal tire cord in thefield of vehicle tires. Several years accumulated data of road testresults using truck tires that were fabricated with nylon cords showfailure patterns unlike any that were associated with previous tests ofrayon tire cords. The failure of nylon truck tire cords may beattributed to nylon fusion, Test data show conclusively that this fusionof the nylon cord is a direct result of the intense heat build-up on theinside of the tire. In a truck tire the presence of nylon fusion isespecially of interest since a truck tire is normally subject to moresevere usage than is a passenger or automotive tire, consequently, nylonfusion is more prominent in the truck tire industry, and it is assumingthe stature of a major problem in passenger tires because of the manylaw suits filed wherein said delitescent defect is a major 4cause offailure.

The problem of nylon fusion is particularly dangerous in addition tobeing expensive for the fusion cannot be detected by one unskilled inthe art since close examination of the tire interior is required todetect the beginning of the fusion process. Usually the occurrence ofnylon fusion, or at least the effect thereof, is realized when the tireexplodes. The problem is well hidden for it required several hundredattempts by patentee in a carefully controlled test program to discoverthe reason for this phenomenon. The problem is becoming acute and is-beginning to be recognized as the source of great loss vof life andproperty, for one may be driving along at a low rate -of speed in closeproximity to pedestrians and experience a violent tire explosion. Thisexplosion may occur at any speed, after any length of driving, underalmost any severity of driving conditions.

There is an area in the shoulder of a truck tire where a maximum amountof bending or flexing takes place. This area may be very narrow Iorsharp, depending upon the design and construction features of the tire.In a well designed tire, this area of maximum flexing is spread over agreater width than a tire of inferior construction. In nylon tires,discoloration on the interior of the tire develops along this area ofmaximum exing. The intensity of the heat-buildup and theA sharpness ofthe flex line control the appearance of the discoloration or heat bandwhich may vary in appearance from `a light reddish brown to nearly blackand vary in wvidth from Eone-half to three 3,397,729 Patented Aug. 20,1968 ICC inches or more. Ina well designed tire, heat bands may notappear or ifvthey do appear they may be relatively broad and indistinct.In better designed tires the heat bands are very broad and haveindistinct edges and in some instances the two heat bands may actuallygrow so broad as to unite in the tire crown, forming a continuousdiscolored area extending from shoulder to shoulder of the tire. In apoorly designed tire these heat bands may be concentrated in a pair ofcontinuous narrow bands which seen to indicate a more intense conditionof nylon fusion that will accordingly bring about a more rapid failure.In the iield of truck tires very few nylon tires fail to develop heatbands. In the eld of passenger tires only a moderately few tiresactually develop inside heat bands.

A nylon tire which indicates excessive heat build-up by the abovementioned heat bands is in a state of advanced deterioration since thenylon cord has undergone some degree of chemical or physical change.Such a tire may continue to run some indeterminable period, but it isonly a matter of time until it will explode. Should the heat bandsappear late in the tread life, so as to enable the tire to live to berecapped, such a tire Would in all probability fail prior to the time atwhich it might be anticipated to wear out.

Nylon fusion may be attributed to any combination of several factorsthat result in a change in the cord, as a consequence of long timeexposure to temperatures generated bythe running tire. One, the nyloncord can be undergoing both a chemical and physical change. Two, the dipcoat that acts as the bond between the nylon ilaments and the rubberskim compound can be undergoing such a change. Or, three, the rubbercompound adjacent to the individual cords can be undergoing a selectiveaging process that results in a hardening of the compound. Anycombination of these factors is termed nylon fusion. It is known thatthe nylon cord on the leading edge of the biased cord loses half itstensile strength under some conditions of service which loss may also bea manifestation of the fusion process.

It is evident that the focal point of attack along the flex line startswith the inside ply of a tire and that this failure progresses outwardthrough the tire, that is, towards the ply adjacent the tread. Once theattack starts, it proceeds at an increasingly rapid rate until theinternal pressure exceeds the external strength of the tire, whereuponthe tire explodes without warning, dismembering the tire along the flexline heat band. The nylon apparently loses a large portion of itsstrength in the inside ply with each successive ply losing a little lessstrength as the deterioration progresses from the inside to the outsideof the tire.

Rayon truck tires have not had the type failures that are characteristicof nylon tires. Tests show that rayon suffers only a slight loss intensile strength after running 100,000 miles or more, when properlyprotected, even though the decomposition temperature of rayon is wellbelow the melting point of nylon. The phenomenon of nylon fusion has notfound its counterpart in the cords of rayon plies. On the contrary,rayon tires generally fail from the outside. Rayon tires are susceptibleto deterioration caused by moisture absorption, whereas nylon appearsimpervious to moisture. Wet rayon loses up to 70% of its dry strength,and as cracks appear, rayon absorbs moisture allowing further crackingand deterioration which results in loss of tensile strength withpossible destruction of the tire. The deleterious and delitescent effectof fusion, change of cord dip chemical, and aging of adjacent rubbercompound is not as evident in the rayon tire as in the nylon tire sincepatentee has found no evidence of the tell-tale heat bands in the rayontires.

In light of the above problems associated with fusion and moisturedeterioration, it appears obvious that both the nylon and rayon tire isnot the panacea, although each embraces desirable qualities, in the tirefield.

It is an object of this invention to provide a vehicle tire having thedesirable performance of nylon cords while avoiding the problemsassociated with nylon fusion.

Another object of this invention is to provide a superior tire that iscapable of withstanding the temperature levels and stresses encounteredunder severe driving conditions.

A further object of this invention is to provide a tire constructionhaving improved traction, reasonably low permanent set, and highresistance to cracking.

Still another object of this invention is to provide an improved biasconstructed tire in which a high energy irnpact resistant cord havinglow bending stiffness and high bending life coupled with excellentresistance to moisture deterioration is used as the principal outsideply cord material. Polyamide exemplifies this material. Rayon, certainpolyesters, and fiberglass possesses superior resistance todeterioration when exposed to heat for long periods of time andaccordingly, are used as the principal inside cord material.

An additional object of this invention is to set forth a novel two plytire utilizing the novel principles of construction outlined herein; and

Other objects of this invention will become apparent to those skilled inthe art from the following remaining disclosure.

FIGURE l shows a conventional four ply tire construction with partsbroken away for clarity.

FIGURE 2 shows a section of a conventional truck tire having eightplies.

Referring to the drawing, and particularly to FIGURE l, referencenumeral 1 indicates the inner or first ply of a biased constructed tirehaving adjacent plies 2, 3, and 4, the fourth ply being adjacent to thetread. Numeral 9 indicates the buifing or scuff rib and numeral 10 themounting guide rib. The first and second breaker plies or strips arerepresented by numerals 11 and 12. T he breaker strips 11 and 12 arefound only in exceptionally heavy duty passenger tires and are notusually fabricated into the ordinary Vehicle passenger tire. Thesebreakers 11 and 12 provide a means of increasing the ply rating of atire.

The buttress of the tire is seen at 13. The tread ribs 15 are separatedby tread grooves 14. Arrows 16 and 17, and 18 indicate the tire iiexingregion. The area between arrows 17 and 19 indicate the tire body. Thebead wire is shown at 21, and 22 is the inner liner compound.

Looking now to FIGURE 2, wherein like numerals are used to indicate likeelements, there is seen a conventional bias constructed truck tire 23having eight plies represented by numerals 1 through 8 wherein numeral 1is the first or inner ply and numeral 8 is the last or outside plyadjacent the tread. Numerals 24 and 25 indicate the area wherediscoloration may first appear on the inside ply of the tire.

A structurally perfect tire, so far as concerns the tire cord textile,is deemed one that has low elongation under load, excellent adhesivepower, high impact energy, excellent bending life, low bendingstiffness, low heat growth, high moisture resistance, and low tendencytowards fusion. No known material exhibits all of these desirableproperties; however, applicant has devised a novel construction whichwill enable fabrication of a tire that, as an end result, embraces theseheretofore unattainable attributes.

Of the known tire cord materials, steel, rayon, including the extra highmodulus rayon; fiber-glass, polyesters, and the polyamides (nylons 6 and66) have achieved the most prominence. Applicants novel tireconstruction employs a combination of these known textiles in a novelarrangement wherein their outstanding properties are utilized whiletheir poor `or mediocre properties are minimized or hidden. This noveltire construction places the materials having high impact energy, highelongation, high adhesive power, long or high bending life, low bendingstiffness,

poor fusion characteristics, and high moisture resistance in the outerplies; and places the materials having the low moisture resistance, highfusion resistance characteristics and low elongation under loads on theinside plies; with materials having properties or characteristicsintermediate of these two extremities being placed in the center orbetween the inner and outer plies.

Of the above materials, the polyamides are best suited for the outsideply material since its bending life far exceeds the others, and itsimpact energy and moisture resistance is highly satisfactory; hence,nylon is used in the below illustrative examples to exemplify an outsideply material having the above outlined desirable properties.

The rubber industry recognizes glass fiber as an interesting andpotentially valuable reinforcing textile for tires. While the iibersuffers interiilament chai-ing failures and fiber-to-rubber adhesionfailure during flexing, the advantages of great strength, resistance tostretch growth, re-

tention of strength above 450 F., non-ammability and chemical inertnesstend to off-set the undersirable features of low impact energy and lowerbending life. Glass cord is only slightly more extensible than steelwhile weighing only one-third as much as steel. The problem of chafingfailures and fber-to-rubber adhesion failures during flexing have beenpartially overcome recently by chemically bonding the individualfilaments of glass to the rubber.

Polyoleiins and polyesters, as reinforcing textiles, offer low cost,good moisture resistance, high strength, and good fatigue resistancematerial to the tire carcass. All of the polyoleiins, except forpolypropylene, have high melting points approaching that of nylon whilepolyester exceeds the melting point of nylon. Adhesion failures, such asfound in liber-glass, is one of the undesirable features associated withthese two textiles.

Rayon, and the extra high modulus rayon, for some reason are essentiallyimpervious to the fusion process. Fiberglass and steel also exhibitresistance to the fusion process. Steel and fiber-glass exhibit verypoor adhesive power, and a low bending life; hence, these materials ofconstruction are best suited for the inside plies where they areprotected from the detrimental effects associated with the outside plylocation. Rayon is used in the below examples as being an exemplicationof the materials of construction suitable for the inside plies.

Ordinary rayon, polyester, and the polyolefins fall in between theproperties outlined above for the inner and outer plies, and hence findutility as the plies adjoining either of the above materials, or thecentral plies.

In this respect, it should be noted that the requirement for lowelongation in the outer ply material is not deemed of prime importancein this novel construction. While this is a departure from the presentaccepted tire manufacturing technique, it is nevertheless considered ofsecondary importance in the selection of an outer ply material since theoutside ply can grow no more than is permitted by the growth of theinside ply material; hence, the requirement of low elongation or lowgrowth rate is shifted to the inside ply which results in a lowering ofthe criticality of elongation of the outer plies.

Improved resistance to separation and resistance to groove cracking areobtained by using a material having low growth properties on the insideplies, simply by the expedient of controlling or restricting tiregrowth.

Since nylon resists the effects of moisture `and shock while rayon,polyester, and fiber-glass resist the effects of high temperature, thepresent novel tire is constructed using rayon, polyester, or fiber-glasscord on the inside plies and using nylon cord on the exterior plies.This results `in a much superior tire than one constructed entirely ofthe above mentioned synthetic cord. The prime advantages of the presentnovel tire is that the heat resistant inner plies are protected againstthe effects of moisture and shock by the outside nylon plies, while themoisture resistant shock resistant nylon is protected from the hightemperatures associated with the inside plies.

It should be understood that the overall characteristics of the tireconstruction using a multi-ply configuration will be related to andgoverned by the relative number of growth and fusion resistant rayonplies used on the inner plies as compared to the number of moistureresistant, high impact energy nylon plies used in the outer pliesincluding the breaker ply. The relationship of these elements must be ofa ratio to first overcome the problem of nylon fusion, followed by thedesirability of low permanent set and the overall ply rating. Thus it isevident that a tire can be fabricated having a minimum of four -pliesand up to as many as fourteen plies with or without breakers to give astrength equivalent to as many plies as desired. In some aircraft t-iresthe number of plies may even exceed this number.

In the instant novel bias constructed truck tire, as in all biasconstructed tires, the adjacent plies run transverse to each other,4noting for example FIGURE 1 wherein ply 1 compared to ply 2 isadjacently and transversely related to each other. Hence, in a properlydesigned tire, each pair of adjacent oppositely biased plies should beof like material since the stresses of the plies on each side of thecomplete tire structure may otherwise be unequal. In a four plyautomotive or truck tire, the two adjacent outer plies 3 and 4 areaccordingly fabricated of nylon cord for example, while the two adjacentoppositely biased inner plies 1 and 2 are fabricated from either rayon,polyester, or fiber-glass. Thus the latter three textiles replace thenylon in an area which is the first to develop signs of heat bands. Inthe instant invention, the nylon plies 3 and 4 are placed in a areawhere they will not be subjected to the effects that cause the fusionprocess, and at the same time provide the rayon, polyester, or berglasswith a moisture barrier and protection from high impact loads. Thus eachmaterial is advantageously placed so as to utilize the outstandingproperties of the material and so as to minimize the the poor propertiesof the materials. In effect, then, the nylon is a moisture and impactbarrier to the rayon, polyester, and fiberglass which in turn serve as aheat barrier to the nylon.

Considering now the eight ply truck tire of FIGURE 2, there is seen foursets of pairs of plies in the biased constructed tire. The adjacentplies are considered in pairs since any two adjacent plies areoppositely biased, and to obtain a structurally balanced tire each sideof the tire must be symmetrically balanced modulus wise. That is, thesame forces must be present in each side of the tire, hence two adjacentoppositely biased plies Ifabricated from identical or closely matchedmaterial will provide a tire with symmetrically balanced forces. Theinstant eight ply tire is therefore advantageously divided into fourpairs of pl-ies, with plies 1 and 2 forming the first pair, plies 3 and4 the next pair, plies 5 and 6 the third pair, and plies 7 and 8 thelast or fourth pair of plies.

Nylon, being highly resistant to deterioration from moisture and havingthe ability to withstand high impact loads, is advantageously used asthe cord fiber in the last pair of plies, number 7 and 8 adjacent thetread.

Fiber-glass may be alternatively used as the reinforcing textile in thetwo adjacent plies furthermost -removed from the tread in the flex areawhere nylon fusion is ordinarily first observed. The excellent abilityof fiberglass to withstand high temperatures makes this choice oftextile ideal for the innermost plies numbers 1 and 2 since theremaining plies will protect the glass fibers from high impact stresses.In such a construction, the central plies preferably are of rayon sincethis material, although unable to withstand the high temperatures aswell as the polyesters and polyolefins (except for polypropylene),exhibits greater ability to withstand exing when properly protectedagainst climatic conditions than do the polyesters and polyolefins.

Five examples of truck tire manufacture:

Example 1 A truck tire having eight plies as in FIG- URE 2 was designedusing nylon cord fiber in the four plies designated by numbers 5, 6, 7,and I8. The next adjacent two plies number 4 and 3 were fabricated usingrayon fiber as the principal reinforcing textile. Plies 1 and 2 werefabricated using a fiber-glass fabric having the individual glassfilaments chemically bonded to the rubber in the ply.

The tire in Example 1 carries fiber-glass at the focal` point of heatbuild-up with rayon plies between the fiberglass and nylon. The rayonplies are protected from external atmospheric conditions by the nylonwhile the nylon is at the same time removed from the area which issubjected to fusion. The superiority of this tire is attributed to theglass being amply protected from impact by the rayon and nylon plies soas to reduce chafing failures and fiber-to-rubber adhesion failures.

Example 2.-Tire was designed using polyester fabric as the reinforcingtextile in plies :number 3 through 6, FIGURE 2. The last two plies 7 and8 were of nylon, as in Example 1, and the first two plies, numbers 1 and2 were constructed of fiber-glass, as in Example 1.

This tire utilized four plies of polyester since this textile isconsidered less efficient, as compared to rayon, in tolerating theeffects of long time heat exposure as encountered in a running tire,while possessing other desirable properties intermediate betweenliber-glass and nylon. Furthermore, the low elongation of polyestercontributes toward a dimens-ionally stable tire.

Example 3.-A four ply truck tire having two breaker plies wasconstructed using a polyamide textile in the two breaker plies 11 and12, FIGURE 1, and in the two plies 3 and 4 adjacent the breaker plies.The inside plies, 1 and 2, were fabricated from an extra high modulusrayon as ply number 1 of FIGURE 1, whose properties were selected toclosely approximate a polyester which was used as the textile in plynumber 2. These two plies, 1 and 2, were carefully selected fromdifferent textile materials, yet the properties -of these two materialswere closely related so as to retain structural symmetry in ply 1 ascompared to ply 2. The rayon versus polyester showed the followingproperties: elongation at 20% breaking load 0.7/1.0; impact energy500/1-800; bending life 1900/4200; heat growth 0.3/0.5. Thus whilemaintaining structural symmetry by adjacent cords having equal modulusheat growth characteristics, an overall improvement in impact energyresistance along with a much higher fatigue resistance has beenaccomplished by the use of the polyesters in ply number 2.

Example 4.-A polyolefin tire cord in lieu of the polyester cord wasdesigned into the central plies numbers 3 through 6, FIGURE 2, as in thepreceding Example 2. Nylon was detained as plies numbers 7 and 8, andfiber-glass was retained as plies numbers 1 and 2, for substantially thesame reasons as outlined above.

Example 5.-A two ply bias constructed tire having a pair of breakerplies was fabricated using nylon in both breaker plies, polyesters inthe ply adjacent the breaker plies, and extra high modulus rayon as theinside ply textile material. The polyester and rayon properties wereclosely matched as in the preceding example.

Example 6.-A two ply bias constructed tire was designed having rayon inply 1 and polyester in ply 2 so as to retain structural symmetry asregards cord modulus and heat growth while enhancing resistance to highenergy impact, and imparting a higher flex life and a lower bendingstiffness than would be realized using two plies of ordinary rayon.

It will be noted in the above examples that a high impact energymaterial having a high bending life along with excellent moistureresistance is always used in the ply adjacent the tire tread and that amaterial having high resistance to heat deterioration is always used inthe plies furthest removed from the tire tread. In applicants copendingcase Ser. No. 504,769, there is set forth a novel vehicle tireconstruction using nylon in the plies adjacent the tread with rayonfabric as the textile in the plies furthest removed from the tread. Thepresent novel tire construction carries the process of eliminating nylonfusion a step further in ordei` to give the maximum benefit of materialsof construction presently available in the truck tire field.

It is considered within the comprehension of this invention to relocatethe various textile materials with respect to each other, or, for thatmatter, to eliminate one of the ply textile materials so long as theconcept of choosing the relative position of the ply material is carriedout by the novel practice outlined herein. However, the novel solutionto eliminating nylon tire explosions due to deterioration at the exline, so as to avoid nylon fusion is best practiced from a considerationof the appended claims which are to be considered the metes and boundsof this invention.

I claim:

1. In a tire having a tread compound forming an outer contacting treadsurface and adapted to be suitably mounted upon a rotated wheel, theimprovement comprisd ing a built up carcass of cord-reinforced plies onthe inner periphery of the tread compound, the cords of saidcordreinforced plies adjacent the tread compound being constructed of amoisture resistant high impact energy material including a polyamide, asthe principal reinforcing fiber the cords of the next adjacentcord-reinforced plies being constructed of an extrudible synthetictextile having resistance to fusion, including rayon; and the innermostof said cord reinforced plies being constructed of berglass as theprincipal cord reinforcing material.

2. A bias constructed vehicle tire having a carcass built up of multipleplies and a ground contacting tread portion on the outer periphery ofthe carcass, each said ply being made of a cord ber as the principal plyfabric, the iiber of the plies adjacent the tread being made ofpolyamide, the ber of the next adjacent plies being made of polyolens,and the fiber of the sub-adjacent and remaining innermost plies beingmade of fiberglass.

3. A pneumatic tire having a carcass built up of multiple biasconstructed plies and a ground contacting tread portion on the outerperiphery of the carcass, each said ply including a textile fibercomprised of a melt extrudible synthetic textile and having theproperties of both extensibility and compressibility in the direction ofeach 'fiber length, the fiber in said ply adjacent said tread and thefiber in said ply sub-adjacent said tread being comprised of nylon asthe principal textile fiber material, the fiber in said ply furthestremoved from said tread and its adjacent ply being fabricated of glassiibers chemically bonded to the rubber of the last said plies, and atleast two oppositely biased plies located between said nylon plies andsaid glass plies, said two oppositely biased plies being made of a cordselected from the group consisting of rayon, polyesters, andpolyolefins.

4. A pneumatic tire comprising a carcass made up of cord-reinforcedplies and a ground-contacting tread portion on the outer periphery ofsaid carcass, the portion of said cord-reinforced plies adjacent saidtread portion having cords made of a polyamide, the cords of the pliesfurtherest removed from said tread being made predominantly ofber-glass, and the remaining cord-reinforced plies between the polyamideand fiber-glass cords being made of rayon.

5. In a pneumatic tire including a carcass of six plies and having aground contacting tread portion peripherally surrounding said carcass,the improvement comprising an innermost biased constructed irst andsecond ply, a biased constructed third and fourth ply adjacent said rstand second ply, an outermost fifth and sixth ply adjacent said third andfourth ply, said fifth and sixth plies being constructed of a textileconsisting of nylon as the principal reinforcing fiber, said third andfourth plies being constructed of rayon as the principal reinforcingfiber, and said first and second plies being constructed of fiberglassas the principal reinforcing fiber.

6. The pneumatic tire of claim 3 wherein said two oppositely biasedplies are made of rayon.

7. The pneumatic tire of claim 3 wherein said two oppositely biasedplies are made of polyester.

8. The pneumatic tire of claim 3 wherein said two oppositely biasedplies are made of polyoleiins.

References Cited UNITED STATES PATENTS 7/1961 Vittorelli 152-356 4/1967Marzocchi 152-359 ARTHUR L. LA POINT, Prz'mazy Examiner.

